The use of robots has increased dramatically in recent years. In industry, robots are increasingly used in a wide variety of applications which require manipulation of hazardous objects, or manipulation of objects in hostile environments. For example, robots have been introduced to safely and reliably handle hazardous payloads, such as chemical or high explosive munitions, in order to reduce exposure to the risks that would occur to human operators if they directly performed the weapons handling. Additionally, robots have been designed which can reliably operate in environments that are relatively hostile to man. As can be appreciated, the robots used in industry are typically multipurpose devices which often must be capable of grasping a wide variety of articles. To this end, robotic devices are provided with end-of-arm toolings, commonly called end effectors, which are used to grasp the article or articles to be manipulated or transported. To be effective, end effectors should be compliant, i.e. be sufficiently flexible to safely and reliably engage articles which are positionally mismatched vis-a-vis the end effector. In addition to having an acceptable degree of compliance, end effectors must also be capable of establishing a relatively high degree of stiffness to prevent undue swaying or swinging of an article once the article has been grasped. Obviously, achieving both characteristics in a single end effector can be a complicated problem, given the mutually exclusive natures of compliance and stiffness.
A number of devices have been suggested which attempt to satisfy the compliance requirement, while maintaining acceptable degrees of stiffness. One genre of such devices is linear ball bushings. Such devices typically comprise ball bushings disposed on precision shafting to provide for substantially frictionless compliance between a robot and the article to be manipulated. Linear ball bushings, however, have several drawbacks. For example, a complete set of bearings and shafting is needed for each required axis of compliance. This effector apparatus, Moreover, exposed bearing shafts are subject to contamination and corrosion which can hinder free motion of the bearings along the shaft. Similarly, other types of end effector mechanisms well known in the pertinent art such as parallelogram linkages and angular spring centering devices, are often bulky and complex mechanisms.
An effective and relatively simple end effector apparatus that provides for adequate compliance in both the vertical and horizontal axes is the suspension cable end effector. Typically, this type of compliance mechanism uses high strength cabling, such as stainless steel aircraft cables, to connect a robot to an article gripping device. In addition to the cable, structure must be provided to adequately stiffen the end effector for transporting or manipulating an article, once the article has been gripped. Ideally, the stiffening structure is releasable before and after article manipulation, to provide for sufficient compliance when gripping potentially misaligned articles or releasing the articles to an unsupported location.
In addition to the above compliance and stiffness considerations, end effectors should also ideally provide for protection against inadvertent crashes of the end effector into surrounding equipment or articles which are to be manipulated. Moreover, in hostile environments, such as are often encountered in the demilitarization of certain types of warheads, end effectors must withstand exposure to corrosive chemical agents such as liquid nitrogen, sodium carbonate or sodium hypochlorite.
Further to the above discussion, an object of the present invention is to provide a robotic end effector tooling apparatus which provides adequate compliance between a robot and an article to be manipulated. Another object of the present invention is to provide a robotic end effector tooling apparatus which is capable of being made sufficiently stiff to prevent undue relative motion between the robot and a gripped article. Additionally, an object of the present invention is to provide a robotic end effector tooling apparatus which can withstand relatively severe crashes. Still another object of the present invention is to provide a robotic end effector tooling apparatus which is capable of remote operation in a hostile environment. Finally, the present invention recognizes a need to provide a robotic end effector tooling apparatus which is relatively simple in construction and which is cost effective to make and use.